JPH08249667A - Signal-processing device of optical disk apparatus - Google Patents

Abstract

PURPOSE: To enable high-density recording/reproduction of signals and simplify the constitution of an apparatus, by selecting one of outputs of two means sampling reproduction signals in accordance with a first or second clock corresponding to a front or rear edge of a mark of an optical disk. CONSTITUTION: A laser light irradiates an optical disk. A reproduction signal RF related to a mark formed on the optical disk is obtained from the reflecting light. The signal RF is binarized by a comparator 2 to a DRF signal. A clock (LCLK) synchronized with a rise of the signal DRF is generated at a PLL circuit 3, and a clock (TCLK) synchronized with a fall of tone signal DRF is generated at a PLL circuit 4. These clocks are inputted to A/D converters 5, 6 which sample the reproduction signal RF in accordance with the signals. On the other hand, a differential circuit 7 differentiates the reproduction signal RF. A comparator 8 binarizes a differential waveform with a predetermined value, and outputs an H output SEL to a selector 9. The selector 9 selects either of the A/D conversion results of two systems in accordance with the output SEL.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal reproducing device of an optical disk device for high density recording / reproducing.

[0002]

2. Description of the Related Art In recent years, the PRML system has attracted attention as a method for increasing the density of disk devices. This is a combination of partial response (PR) and maximum likelihood decoding (ML), and it is possible to reproduce signals with few errors even when the band of the signal reproduction system is narrow and there is much noise. As a result, there is an advantage that the linear recording density is improved.

Regarding PRML, for example, "High density of magneto-optical disk by partial response using Viterbi decoding" (The Institute of Electrical Engineers of Japan, Magnetics Research Group MAG-9)
2-191). The data reproduction by the Viterbi decoding method is a method for selecting and detecting the most probable data series based on the information (correlation in the time axis direction) of the transition state of the reproduction signal (RF signal), and it results in higher density by signal processing. Various methods have been studied.

By the way, in a method of recording by optical modulation such as a magneto-optical disk or a phase change disk, it is not possible to form a mark with a correct length on the disk due to laser power fluctuation at recording or environmental temperature fluctuation. In some cases, there is a drawback. This does not matter so much in the mark position recording in which the mark position (presence / absence) corresponds to "1" of data, but the data position changes in the mark edge recording in which the mark edge corresponds to "1". Therefore, the margin at the time of decoding becomes small.

As a method for compensating for this, for example, Japanese Patent Laid-Open No. 2-
In Japanese Patent No. 183471, two series of clocks corresponding to the leading edge (leading edge) and the trailing edge (trailing edge) of a mark on a disk are used, the leading edge and the trailing edge are discriminated independently, and then combined. Then, the method of decoding is disclosed.

Even when high density recording / reproducing is performed using PRML, when data recording (writing) is performed by an optical modulation method, if the mark length cannot be formed correctly, reproduction is performed near the edge during reproduction. This is a problem because the signal level fluctuates. However, the above-mentioned Japanese Patent Laid-Open No. 2-1
The method described in Japanese Patent No. 83471 considers that the reproduced signal is "1" every time the reproduced signal crosses the zero level.
It cannot be applied unless it is a so-called bit by bit decoding method.

Therefore, in Japanese Patent Laid-Open No. 6-150578, a reference area is provided in a specific area on the disc (about one location in one sector), and a specific pattern is recorded in the reproduction area in PRML. In this regard, a method has been proposed in which a variation in the mark length is detected from the reproduction signal level during reproduction, and correction is performed during maximum likelihood decoding.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The method described in Japanese Patent No. 50578 aims to correct the fluctuation of the mark length, which is originally a timing shift, by adjusting the level of the reproduction signal, and finally cancels the effect of the fluctuation of the mark length completely, and at the time of decoding. It can be said that it is difficult to secure a margin.

Further, with this method, correction can be performed only at the frequency at which the reference area appears. Even in the same sector, the amount of mark length deviation changes due to uneven sensitivity in an actual disk.Therefore, even if calibration is performed in the reference area, the mark length deviation changes in the middle of the sector, leaving level fluctuations in the reproduced signal. There is a case that the margin cannot be secured at the time of decoding. To prevent this, the reference area may be increased, but this causes a problem that the recording area that can be used by the user decreases.

The present invention has been made in view of the above problems. In the optical modulation type PRML, it is possible to use two clocks independent of the front and rear edges, and the recording area usable by the user is sacrificed. PRML capable of high-density recording and reproducing
It is an object of the present invention to provide a signal reproducing device which can be combined with the above to construct an optical disc device having a large storage capacity at a low cost.

[0011]

According to the present invention, an optical disc is irradiated with a light beam, a reproduction signal associated with a mark formed on the optical disc is detected from the reflected light, and recording is performed based on the reproduction signal. A signal reproducing device of an optical disc device for reproducing data, comprising: a first clock generating means for generating a first clock corresponding to a front edge of the mark; and a second clock corresponding to a rear edge of the mark. Second clock generating means for generating, first sampling means for sampling the reproduction signal according to the first clock, second sampling means for sampling the reproduction signal according to the second clock,
Selection means for selecting either the output of the first sampling means or the output of the second sampling means.

The first and second clock generating means generate a first clock and a second clock respectively corresponding to the leading edge and the trailing edge of the mark on the disk, and the first and second sampling means forward the clock. The reproduced signals are sampled according to the clocks in phase with the edges and the rear edges, respectively. Then, by selecting either the output of the first sampling means or the output of the second sampling means by the selection means, sampling is performed at optimum timing at each of the front edge and the rear edge. Done, and accurate sampling results are obtained.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 relate to a first embodiment of the present invention, FIG. 1 is a block diagram showing a configuration of a signal reproducing device, FIG. 2 is a timing chart showing an operation of the signal reproducing device, and FIG. It is explanatory drawing which shows the structural example and operation | movement of the selector provided.

In this embodiment, a signal reproducing apparatus provided in an optical disk apparatus for recording by the optical modulation method and reproducing by using PRML in which the partial response method (PR) and the maximum likelihood decoding (ML) are combined. It shows a configuration example.

The signal reproducing apparatus 1 is a first comparator 2 for binarizing a reproduced signal and a first clock generating means for generating a clock (LCLK) synchronized with the rising edge of the output of the comparator 2. A PLL circuit 3; a second PLL circuit 4 as a second clock generating means for generating a clock (TCLK) synchronized with the falling edge;
A reproduction signal is generated by the second PLL circuit 4 and a first A / D converter 5 as first sampling means for A / D converting the reproduction signal by the clock generated by the first PLL circuit 3. Second A / D converter 6 as second sampling means for A / D converting with clock
A differentiating circuit 7 for differentiating the reproduction signal, a second comparator 8 for binarizing the output of the differentiating circuit 7, and a first A / D
The converter 5 and the selector 9 as a selection unit that selects one of the outputs of the second A / D converter 6 by the output of the second comparator 8.

The operation of the signal reproducing apparatus 1 of this embodiment is shown in FIG.
Will be described with reference to.

Here, a case where the data to be recorded on the disk is the data as shown in FIG. 2A will be described assuming that PR (1,1) is used for the partial response method of recording and reproduction.

The recording data is modulated by a precoder having a characteristic opposite to that of PR (1,1), and becomes the data shown in FIG. Specifically, since the PR (1,1) precode is an XOR (exclusive OR) of the bit after the immediately preceding precode and the current data bit, that is, NRZI conversion, the data bit is '1'. Whenever appears, the data after precoding is from "0" to "1" or "1"
Will be inverted to '0'.

Writing to the optical disk is performed so as to form a mark at the portion "1" after this precoding, so that the writing signal is as shown in FIG. When viewed from the original data (FIG. 2A), the edge corresponds to the "1" portion of the data.

Writing to the disc is performed in accordance with this recording signal, and as shown in FIG.
It is assumed that a mark slightly longer than intended is formed.
This is likely to occur when the ambient temperature is high, the sensitivity of the disc is high, or the laser output for recording is high.

When such marks are reproduced by irradiating them with laser light, a reproduction signal RF as shown in FIG.
Is obtained. This reproduced signal is binarized by the comparator 2 at a predetermined value (for example, zero level), and becomes the DRF signal shown in FIG. The clock (LCLK) synchronized with the rising edge (front edge) of the binarized signal DRF is PL.
A clock (TCLK) generated by the L circuit 3 as shown in FIG. 9G and synchronized with the falling edge (rear edge) is generated by the PLL circuit 4 as shown in FIG. These clocks are supplied to the A / D converter 5 respectively.
And 6 are supplied.

The A / D converters 5 and 6 sample the reproduction signal RF shown in FIG. 2E according to the supplied clock. The sampling timing is LCL
It is determined by K or TCLK, and becomes the one corresponding to the rising or falling of the reproduction signal, respectively. The result of sampling by the A / D converter 5 in synchronization with LCLK is D10 to D19 (FIG. 2 (h)), TCL.
It is assumed that the results of sampling by the A / D converter 6 in synchronization with K are obtained as D20 to D29 (FIG. 2 (j)). Actually, the A / D in the A / D converters 5 and 6
The conversion is performed in about 6 to 8 bits.

On the other hand, the differentiating circuit 7 differentiates the reproduction signal RF to form a waveform as shown in FIG. This differential waveform is binarized at a predetermined value (for example, zero level) by the comparator 8 to obtain an output (SEL) that becomes'H 'when the differential signal is positive as shown in FIG.

Then, the selector 9 follows the output SEL of the comparator 8 and outputs the two series of A / D conversion results (see FIG. 2).
Either (h) or (j) is selected. The purpose of this selection is to select the A / D conversion result sampled at a more accurate timing at the edge portion of the mark and pass it to a decoding circuit (Viterbi decoding circuit, etc.) in the subsequent stage (not shown). Then LC in sync with the front edge
The result of sampling by LK ((h) in the same figure) and the result of sampling by TCLK in synchronization with the rear edge ((j) in the same figure) may be selected near the rear edge. In the other part, that is, in the part where the reproduced waveform is flat apart from the edge, either one may be selected.

In the present embodiment, the selector 9 refers to the output SEL of the comparator 8 at the rising edge of LCLK ((g) in the figure) synchronized with the front edge, and the output SEL of the comparator 8 is "H". Is the result of sampling with LCLK, and when it is'L ', TCLK
The result sampled in shall be selected. Therefore, the output of the selector 9 becomes as shown in FIG.
This signal is output as the A / D conversion result of the reproduction signal.

The selector 9 is, for example, as shown in FIG.
Output S of comparator 8 at the rising edge of LCLK
It is configured to have a flip-flop 10b that outputs EL, and a register 10a that stores the two series of A / D conversion results by LCLK and TCLK and the output SEL of the comparator 8 at the rising edge of LCLK in parallel. The selector 9 includes two series of A / D converters from the A / D converters 5 and 6.
The D conversion result and the output SEL of the comparator 8 are respectively stored in the register 10a, and the A / D conversion result (the one surrounded by a circle in the figure) is obtained from either register while referring to the value of SEL later. Just take it out.

The A / D conversion result of the reproduced signal selected by the selector 9 in this manner is sent to a decoding circuit (not shown) in the subsequent stage, and the decoding circuit performs maximum likelihood decoding such as Viterbi decoding. In the present embodiment, sampling is independently performed at the front and rear edges by clocks in phase with the front edge and the rear edge of the reproduced signal, and these sampling results are combined and sent to the decoding circuit. Maximum likelihood decoding is enabled. Since a kind of error correction can be performed by the maximum likelihood decoding, it becomes possible to cope with higher density recording / reproduction as a result.

As described above, according to this embodiment,
Use the clock synchronized with the leading edge and the clock synchronized with the trailing edge at the timing suitable for each edge.
Since A / D conversion is performed and one A / D conversion result is selected and output to the decoding circuit based on the result of binarizing the differential signal of the reproduction signal, the A / D conversion result passed to the decoding circuit Is always sampled at the optimum timing with respect to the reproduced waveform, and the margin at the time of performing maximum likelihood decoding is increased, so that it is possible to cope with higher density recording and reproduction. Further, as the margin at the time of decoding increases, the mark length variation is allowed at the time of recording, so that the configuration of the recording system can be particularly simplified and the cost of the apparatus can be reduced.

Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram showing the configuration of the signal reproducing device according to the second embodiment, and FIG. 5 is a timing chart showing the operation of the signal reproducing device according to the second embodiment.

In the first embodiment, the configuration in which two clocks having the same phase for the front edge and the rear edge are used has been described, but in the second embodiment, in addition to the two clocks, an intermediate clock between these clocks is used. The structural example which further uses the 3rd clock which has a phase is shown.

The signal reproducing apparatus 11 of the second embodiment is similar to the signal reproducing apparatus of the first embodiment shown in FIG. 1 except that the PLL circuits 3 and 4 and the A / D converters 5 and 6 are connected in parallel. PLL circuit 12 and third A / D converter 13
Is additionally provided, and the operations of the comparator 8 and the selector 9 are changed to form the comparator 8a and the selector 9a. The same parts as those in the first embodiment are designated by the same reference numerals.

The operation of the signal reproducing apparatus 11 of this embodiment will be described with reference to FIG. Since FIG. 5 shows the operation in the case of the same recording data as in the first embodiment, the description of the common part will be omitted.

Similar to the first embodiment, LCLK (FIG. 5 (g)) and T are generated by the PLL circuits 3 and 4, respectively.
CLK (FIG. 5 (i)) is generated, and based on these clocks, A / D converters 5 and 6 are used to generate CLK (FIG. 5 (i)).
An A / D conversion result as shown in (j) is obtained.

At the same time, the third PLL circuit 12 binarizes the reproduction signal and outputs the output DRF of the comparator 2 (see FIG. 5).
Both the rising and falling edges of (f) are input,
As a result, a clock MCLK having an intermediate phase between the clock (LCLK) synchronized with the rising edge and the clock (TCLK) synchronized with the falling edge as shown in FIG.
Occurs. This clock is input to the third A / D converter 13, and the A / D converter 13 samples the reproduction signal RF according to this clock. This M
The A / D conversion results synchronized with CLK are D30 to D39 ((l) in the figure).

On the other hand, the comparator 8a has a reproduction signal RF.
The differential signal (FIG. 5 (m)) of which the output becomes'H 'when the differential signal is positive and the output becomes'H' when the differential signal is negative are arranged in parallel. Therefore, SEL1 ((n) in the figure) and SEL2 ((o) in the figure) are obtained as the output of the comparator 8a.

The selector 9a has three A / S based on the two output signals SEL1 and SEL2 from the comparator 8a.
One of the outputs of the D converters 5, 6 and 13 is selected. In order to select the A / D conversion result sampled at the optimum timing, the output of the A / D converter 5 is near the leading edge, the output of the A / D converter 6 is near the trailing edge, and the A / D conversion is at other portions. The output of the D converter 13 may be selected.

Therefore, in this embodiment, if the output SEL1 of the comparator 8a is "H" at the rising edge of LCLK (FIG. 5 (g)) synchronized with the leading edge, the output of the A / D converter 5 is synchronized with the trailing edge. The output SEL of the comparator 8a at the rising edge of TCLK ((i) in the figure)
When 2 is'H ', the output of the A / D converter 6 is selected, and in other cases, the output of the A / D converter 13 is selected. Therefore, the output of the selector 9a is shown in FIG.
It becomes as shown in.

Then, as in the first embodiment, the A / D conversion result of the reproduction signal selected by the selector 9a is sent to a decoding circuit in the subsequent stage (not shown) for decoding.

As described above, in this embodiment, a clock having an intermediate phase between the leading edge and the trailing edge is generated, and the A / D conversion result sampled by this clock is selected in the portion other than the edge of the mark to select the decoding circuit. Since the data is output to and decoding is performed, the sampling of the reproduction signal can be brought closer to the optimum timing than in the first embodiment, the margin at the time of decoding is increased, and higher density recording and reproduction can be performed. There is.

Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram showing the configuration of the signal reproducing device according to the third embodiment.

Each of the above-described embodiments has been described as an example applied to an apparatus in the case where the optical disk is a continuous servo format (a system in which tracking is performed by a guide groove and a clock for reproduction is taken out from the data itself on the disk). However, since the present invention can be applied even in the case of the sample servo format, a configuration example in this case will be shown as a third embodiment. The sample servo method is a PLL based on a specific pit called a clock pit on the disk.
The channel clock is regenerated by, and all operations such as recording and reproduction are performed based on this channel clock.

The signal reproducing apparatus 21 of the third embodiment includes a clock pit extraction circuit 22 for extracting a portion corresponding to a clock pit on a disc from a reproduced signal, and a PLL for reproducing a channel clock from the extracted clock pit.
The circuit 23 and a first clock generation circuit 24 that generates a clock (LCLK) in phase with the front edge of the reproduction signal based on the channel clock generated by the PLL circuit 23.
And a second clock generation circuit 25 for generating a clock (TCLK) in phase with the rear edge. Then, similarly to the first embodiment, the A / D converters 5 and 6, the differentiating circuit 7, the comparator 8 and the selector 9 are provided.

In the case of a magneto-optical disk, a sum signal (a signal proportional to the intensity of reflected light) of the reproduction signal output from the photodetector is used for clock pit extraction, and a difference signal (a signal on the surface of the disk is used for reproducing data) Signal proportional to the car rotation angle) is used.

The channel clock regenerated by the PLL circuit 23 is input to the clock generation circuits 24 and 25, and the clocks LCLK and TCLK in phase with the front edge and the rear edge of the regenerated signal are generated by moving the phase. . If the same operation as in the first embodiment is performed in accordance with these two clocks, the reproduction signal value can be sampled at the optimum timing for each of the front edge and the rear edge.

For clock phase matching in the clock generation circuit 24 or 25, for example, a specific pattern is always recorded at the beginning of a sector, and the differential signal of the reproduction signal in the specific pattern portion is changed while gradually changing the clock phase. The phase at which the amplitude of the differential signal becomes maximum after sampling is used as the phase of the clock in that sector. The phases of the two clocks can be changed, for example, by changing the delay amount with respect to the original clock reproduced from the clock pits by changing the programmable delay line.

As other clock phase matching methods, various methods are conceivable, such as controlling the phase of each clock as needed so that the second-order differential signal of the reproduced signal becomes zero level. For example, it is described in Japanese Patent Application No. 5-265199 and Japanese Patent Application No. 6-105778.

As described above, according to this embodiment,
Even when recording is performed on the optical disc of the sample servo format by the optical modulation method and reproduction is performed using PRML, the front edge of the mark formed on the disc,
Since it is possible to sample the reproduced signal at the optimum timing for each rear edge, it is possible to take a larger margin when performing maximum likelihood decoding later, and use this margin to achieve higher density recording and reproduction. It becomes possible to do.

Next, a fourth embodiment of the present invention will be described. FIG. 7 is a block diagram showing the configuration of the signal reproducing apparatus according to the fourth embodiment, and FIG. 8 is a timing chart showing the operation of the signal reproducing apparatus of the fourth embodiment. In addition,
The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the first embodiment, when one of the reproduced signal values A / D converted at the timing synchronized with each of the front edge and the rear edge is selected, the differential signal of the reproduced signal is used for selection. In the fourth embodiment, a configuration example using the difference between the reproduction signal values after A / D conversion is shown.

The signal reproducing apparatus 31 of the fourth embodiment is such that the differentiating circuit 7 is deleted from the signal reproducing apparatus 1 of the first embodiment shown in FIG. 1, and the memory 32 as a storage means and the subtraction as an arithmetic means. And the operation of the comparator 8 is changed to form a comparator 8b.

In this configuration, the memory 32 stores the previous value of the reproduced signal value sampled by the A / D converter 5, and the subtractor 33 stores the current (latest) sampling result by the A / D converter 5 and the memory 32. Calculate the difference from the stored previous value. In addition, the comparator 8b
Outputs "H" as an output signal SEL when the result of the subtraction by the subtractor 33 is positive, and when the result of the subtraction is negative or zero.

The operation of the signal reproducing apparatus 31 of this embodiment will be described with reference to FIG. Since FIG. 8 shows the operation in the case of the same recording data as in the first embodiment, the description of the common part will be omitted.

Similar to the first embodiment, LCLK (FIG. 8 (g)) and T are generated by the PLL circuits 3 and 4, respectively.
CLK (FIG. 8 (i)) is generated, and based on these clocks, A / D converters 5 and 6 are used to generate (CLK) in FIG.
An A / D conversion result as shown in (j) is obtained. At this time,
In the subtractor 33, the previous value and the current value of the reproduction signal value sampled by the A / D converter 5 are subtracted, and the subtracter output as shown in FIG.
From the comparator 8b, an output SEL which becomes "H" when the subtractor output is positive is obtained as shown in FIG. Then, according to the output SEL of the comparator 8b, the selector 9 selects and outputs one of the two series of A / D conversion results (FIGS. 8 (h) and 8 (j)) as shown in FIG. To do.

That is, near the front edge of the mark, the output of the subtractor 33 becomes positive (maximum), the output SEL of the comparator 8b becomes "H", and is sampled by the clock (LCLK) synchronized with the front edge. The output of the A / D converter 5 is selected by the selector 9. Also,
Near the trailing edge of the mark, the output of the subtractor 33 becomes negative (minimum), the output SEL of the comparator 8b becomes'L ', and the A / D converter 6 sampled by the clock (TCLK) synchronized with the trailing edge. Is selected by the selector 9. Then, the A / D conversion result of the reproduction signal selected by the selector 9 is sent to a decoding circuit in the subsequent stage (not shown), and decoding is performed.

As described above, according to the present embodiment, the memory for storing the sampling value of the past reproduction signal is provided, and the calculation is performed between the present sampling value and the past sampling value stored in the memory. , A sampled at the timing synchronized with each of the leading edge and the trailing edge
Since which sampling value of the / D conversion result is used for decoding is selected, it is not necessary to externally provide a reproduction signal differentiating circuit or the like for this selection. Therefore, in addition to the effects of the first embodiment, simplification of the circuit is possible, and at the same time, it is not necessary to use a differentiating circuit which is easily affected by noise and which may cause malfunction, so that reliability can be improved.

In the present embodiment, the A / D conversion result to be selected is determined based on the difference between the previous sampling value and the latest sampling value of the reproduced signal. You may go.
However, in order to further reduce the circuit scale, it is desirable to perform an operation to obtain the difference from the previous value.

The object for which the difference is calculated does not necessarily have to be the results sampled in synchronization with the leading edge, but may be the difference between the results sampled in synchronization with the trailing edge or the sampling result selected by the selector. It may be a difference from the result of sampling in synchronization with one edge.

In the above embodiments, the case where the mark on the disk is formed long has been described. However, when the mark is formed shorter due to lack of power or the like, the clock of the front edge and the clock of the rear edge are formed. However, the signal reproduction apparatus described above can be used as it is.

Further, although the case where the PR (1,1) system is adopted as the partial response has been described in the present embodiment, the present invention can be similarly applied to other systems. For example, the target of maximum likelihood decoding by sampling with the A / D converter may be a differential signal of the reproduction signal, and the equalization method may be PR (1, 0, -1) or the like.
Alternatively, the present invention can be similarly applied to the conventional mark edge recording which is not a partial response.

Further, in the present embodiment, the reproduction signal RF is directly inputted to the comparator and the PLL is constructed for its output to generate the clock. However, the noise is removed through an appropriate filter and then inputted to the comparator. You can Alternatively, instead of inserting a filter immediately before the comparator, the reproduction signal RF itself may be passed through the filter and the reproduction signal after filtering may be input to both each A / D converter and the comparator. Alternatively, filters having different characteristics may be arranged immediately before the respective A / D converters and comparators.

The signal to be referred to when one is selected from a plurality of sampling results is not limited to the differential signal of the reproduction signal, but may be a differential signal or any other signal that has a maximum or a minimum at the edge portion of the mark. A decision can be made.
Further, the judgment of the mark edge portion may be made based on the result of comparison with a value slightly offset, instead of being compared with the zero level.

[Additional Notes] As described in detail above, according to the embodiment of the present invention, the following configuration can be obtained.
That is, (1) a signal of an optical disk device for irradiating an optical disk with a light beam, detecting a reproduction signal associated with a mark formed on the optical disk from the reflected light, and reproducing recorded data based on the reproduction signal. A reproducing apparatus, first clock generating means for generating a first clock corresponding to a front edge of the mark, and second clock generating means for generating a second clock corresponding to a rear edge of the mark. A first sampling means for sampling the reproduction signal in accordance with the first clock; a second sampling means for sampling the reproduction signal in accordance with the second clock; and an output of the first sampling means, or Selection means for selecting one of the outputs of the second sampling means. Signal reproducing apparatus of the disk drive.

According to this structure, even if the mark edge position changes due to the change in the length of the mark on the disk, sampling is performed at the optimum timing by the clocks in phase with the front edge and the rear edge. Since an accurate sampling result can be obtained at the edge portion, the margin at the time of later decoding becomes large, and high-density recording / reproducing can be performed by utilizing this margin. Further, since the mark length variation is allowed at the time of recording, there is an effect that the configuration of the recording system can be particularly simplified and the cost of the apparatus can be reduced.

(2) The optical disc is irradiated with a light beam,
A signal reproduction device of an optical disk device for detecting a reproduction signal related to a mark formed on the optical disk from the reflected light and reproducing recorded data based on the reproduction signal, which corresponds to a front edge of the mark. Clock generating means for generating a first clock, second clock generating means for generating a second clock corresponding to the rear edge of the mark, the first clock and the second clock Third clock generation means for generating a third clock having an intermediate phase of, first sampling means for sampling the reproduction signal according to the first clock, and the reproduction signal according to the second clock Second sampling means for sampling, and third sampling means for sampling the reproduction signal according to the third clock It said first, second, or third signal reproducing apparatus of an optical disk apparatus characterized by comprising a selection means for selecting one of the output of the sampling means.

According to this structure, sampling is further performed by using a clock having an intermediate phase of the clocks in phase with each of the front edge and the rear edge, so that the optimum timing is achieved even in the non-edge portion of the mark. Since the result sampled in (1) can be used at the time of decoding, the margin at the time of decoding can be increased and high-density recording / reproducing can be performed.

(3) A signal detecting means for detecting a maximum or minimum signal at the edge portion of the mark is provided.
3. The signal reproducing apparatus for an optical disk device according to appendix 1 or 2, wherein the selecting means operates based on the output of the signal detecting means.

According to this structure, the maximum or minimum signal is detected at the edge portion of the mark, and the sampling result to be used for decoding is selected from a plurality of sampling results based on this signal. The trailing edge can be correctly identified, and an appropriate sampling result can be reliably selected.

(4) It has a binarizing means for binarizing the reproduction signal, and the first clock generating means supplies the clock synchronized with the rising edge of the output of the binarizing means with the second clock. 3. The signal reproducing apparatus for an optical disk device according to appendix 1 or 2, wherein the generating means respectively generate a clock synchronized with the trailing edge of the output of the binarizing means.

According to this structure, the sampling clock is generated based on the timing of the leading edge and the trailing edge detected by binarizing the reproduced signal, so that a clock whose timing matches each edge is always generated. You can

(5) The optical disk has a sample servo format, and the first and second clock generating means generate a clock by moving a phase of a channel clock reproduced based on a clock pit on the optical disk. 3. The signal reproducing device for an optical disk device according to appendix 1 or 2, characterized in that

According to this structure, it is possible to perform sampling in accordance with the positions of the front and rear edges even in the optical disk of the sample servo format, and it is possible to perform high density recording / reproducing.

(6) The signal reproducing device of the optical disk device described in appendix 1 or 2, wherein the characteristics of the reproduced signal conform to the partial response system.

By adopting the partial response system, it is possible to carry out recording and reproduction with higher density.

(7) The signal reproducing device of the optical disk device according to appendix 1 or 2, wherein maximum likelihood decoding is performed on the output sequence of the selecting means.

By performing the maximum likelihood decoding, higher density recording / reproducing can be performed.

(8) The signal reproducing apparatus for an optical disk device according to appendix 3, wherein the signal detecting means differentiates the reproduced signal.

According to this structure, since the front edge and the rear edge are distinguished by differentiating the reproduced signal, the front edge and the rear edge can be correctly discriminated and an appropriate sampling result can be surely selected.

(9) There is a storage means for storing the past output of the first or second sampling means at least back to the previous sampling value, and the signal detecting means has the first or second sampling means. 4. The signal reproduction of the optical disk device according to appendix 3, which outputs a result of calculation between a current sampling value by the sampling means and a past sampling value stored in the storage means. apparatus.

In this configuration, since the calculation result between the reproduced signal values after sampling may be used as the signal to be referred when selecting the sampling result of the reproduced signal, it is not necessary to provide an external differentiating circuit or the like. . Therefore, the circuit can be simplified, and at the same time, the reliability can be improved because it is not necessary to use a differentiating circuit which is easily affected by noise and which may possibly malfunction.

(10) The signal detection means outputs the difference between the current sampling value by the first or second sampling means and the previous sampling value stored in the storage means as the calculation result. The signal reproducing apparatus of the optical disc apparatus described in appendix 9, wherein the signal reproducing apparatus is provided.

The circuit size can be further reduced by using the signal referred to when selecting the sampling result of the reproduction signal as the result of the calculation for obtaining the difference from the previous sampling value.

[0082]

As described above, according to the present invention, even in the PRML of the optical modulation system, it is possible to use two clocks independent of the front and rear edges, without sacrificing the recording area that can be used by the user. The optical modulation system capable of simplifying the device and the PRML capable of high-density recording / reproduction are combined, so that there is an effect that an optical disc device having a large storage capacity at a low cost can be configured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a signal reproducing device according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the signal reproduction device according to the first embodiment.

FIG. 3 is an explanatory diagram showing a configuration example and an operation of a selector provided in the signal reproduction device.

FIG. 4 is a block diagram showing a configuration of a signal reproducing device according to a second embodiment of the present invention.

FIG. 5 is a timing chart showing the operation of the signal reproduction device according to the second embodiment.

FIG. 6 is a block diagram showing a configuration of a signal reproducing device according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a signal reproducing device according to a fourth embodiment of the present invention.

FIG. 8 is a timing chart showing the operation of the signal reproducing apparatus according to the fourth embodiment.

[Explanation of symbols]

 2 ... 1st comparator 3 ... 1st PLL circuit 4 ... 2nd PLL circuit 5 ... 1st A / D converter 6 ... 2nd A / D converter 7 ... Differentiation circuit 8 ... 2nd comparator 9 ... selector

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Claims (1)

[Claims] 1. A signal of an optical disk device for irradiating an optical disk with a light beam, detecting a reproduction signal associated with a mark formed on the optical disk from the reflected light, and reproducing recorded data based on the reproduction signal. A reproducing apparatus, wherein first clock generating means for generating a first clock corresponding to the front edge of the mark, and second clock generating means for generating a second clock corresponding to the rear edge of the mark A first sampling means for sampling the reproduction signal according to the first clock; a second sampling means for sampling the reproduction signal according to the second clock; and an output of the first sampling means, or Selecting means for selecting any one of the outputs of the second sampling means; Signal playback device for disk devices.